A run of the mill GM 4L60E trans. You've done well with it so far. A drain/fill or successive drains/fills at 36-50K is a smart thing to do. 100K would be perfect for a pan drop, magnet cleaning and filter replacement. I've got some experience doing cooler line flushes with newer 4L60E's and it's a two person job if this is what you want to do. You will need clamps and fairly substantial tubing, someone to 'man' the tube/jug and someone to work the ignition. On my 4L60E equipped Trailblazer, it would blast out 1gal of hot ATF in under 10sec! Initially I tried it myself. The hose hooked to my cooler line came close to the top of the gallon jug, blew out and did the crazy-daisy spraying ATF all over the place until I managed to scramble back to the ignition. They're pretty fat/hi flow cooler lines on the trucks, not to mention the GM Pushlock fittings are a joy until you figure them out. It's all totally doable, just wanted to let you know what you're up against.
Joel